Computerized Axial Tomography (CAT) is a revolutionary radiographic method. We have accumulated direct experience with one of the devices used for this technique, the ACTA-Scanner. Assessment of CAT (ACTA-Scanner) in syringomyelia and other diseases of the spinal cord has been accomplished. Comparison of the ACTA-Scanner with another equipment, the British EMI-Scanner, has been carried out and the relative advantages and disadvantages of the two machines have been evaluated. Beam hardening, an important physical parameter in reconstructive transmission tomography has been investigated on a simulated computer model. A thorough analytical review of the various mathematical reconstruction algorithms has been accomplished.